Knockout in Photoshop blending options doesn't work on text after it is saved as .psd.

A few days ago I made a design using some text and graphics and saved it in Photoshop. Today I am trying to use the Knockout option in blending and it doesn't work. The emboss and all other options work but not the knockout, any suggestions please?

Did you remember to drop the Opacity of the layer you're using as the Knockout in the Advanced Blending portion of Blending Options under Layer Styles?

Assuming so, then, as Christoph requested, could you post a screenshot of your document, Layers panel, and Layer Style dialog, so we can get some clear context? It would be nice to share your OS and Photoshop versions as well.